Figure 5.

IDO1-secreted Kyn restrains cellular senescence and exacerbates chemoresistance via attenuating IGFBP5/p53 signaling. (A) Western blot was performed to detect protein levels of p53, p27, p21, and IGFBP5 in HCT-116 and HCT-8 cells after exposure to 100 μM Kyn. (B, C) Relative mRNA expression and protein levels of IGFBP5, p53, p21, and p27 were analyzed by qPCR analysis (B) and western blot (C) in the stable IDO1 overexpressed HCT-116 cells with or without IGFBP5 overexpression. (D) HCT-116 cells overexpressing IDO1 alone or together with IGFBP5 were treated with the indicated concentrations of 5-FU and the cell viability was measured by MTT assay. (E, F) HCT-116 cells were treated with Kyn (100 μM) with or without IGFBP5 overexpression and the indicated protein levels and cell viability were analyzed by western blot (E) and MTT assay (F). (G) Relative levels of p27 were analyzed by western blot in the stable IDO1 overexpressed HCT-116 cells with or without p27 overexpression. (H) HCT-116 cells overexpressing IDO1 alone or together with p27 were treated with the indicated concentrations of 5-FU and the cell viability was measured by MTT assay. (I) SA-β-gal staining of the stable IDO1 overexpressed HCT-116 cells with or without p27 overexpression in the presence of 20 μM 5-FU treatment for 48 h. The SA-β-gal positive cells were calculated. *P < 0.05; **P < 0.01.